For the first time in nearly a generation, Arizona voters will elect a new senator. Republican Sen. Jon Kyl is retiring after 18 years. His ideological successor is Republican Rep. Jeff Flake, and a lot of people expected Flake to have an easy time of it.

But recent polls suggest Democrat Richard Carmona — a former surgeon general and a Hispanic — has a shot at winning. The race has become heated, and the airwaves are filled with brutal ads.

"Many call him the most conservative congressman in Washington," is how one ad proudly describes the Republican, who's from a pioneering Mormon family and who has served in Congress since 2001. The ad, paid for by Flake's campaign, portrays him as an early riser who goes jogging before dawn and prepares breakfast with his family before heading to work. It concludes: "Arizona's battle-tested conservative is Jeff Flake."

If you're into battle-testing, though, Carmona's resume is hard to beat. He was born in New York's Harlem neighborhood of Puerto Rican descent.

One campaign ad features Gary Clark, one of Carmona's Vietnam-era colleagues, describing the candidate as a "poor kid who quit school and got a second chance in the Army, became a doctor, SWAT team leader and surgeon general."

Flake and the Republican Party have been tying Carmona to the Obama administration, not necessarily a helpful connection in a state Republican presidential nominee Mitt Romney is favored to win.

An ad released last month by Flake's campaign says: "Richard Carmona was recruited [to run for Senate] by Barack Obama. Jeff Flake is supported by Jon Kyl and John McCain," Arizona's Republican senators.

Carmona, though, served for nearly four years as surgeon general under former President George W. Bush, a Republican. Until a year or so ago, he was a registered independent.

In the past, he says Republicans also tried to recruit him for office.

"In an old Republican Party, I might have been able to go with a fiscal conservative approach and smaller government. I'm OK with that," Carmona tells NPR. "But when you look at what's happened in our state and the nation and where the Republican Party has gone, most of my friends who are moderate Republican friends are embarrassed that we're attempting to legislate contraception, defunding Planned Parenthood."

Carmona is playing the moderate to Flake's conservative stance. Sensing a possible upset, the Democratic Party has spent at least $1 million on ads portraying Flake as too conservative, even for Arizona. They've attacked Flake's positions on abortion and contraception, and highlighted a few of his votes on veterans.

Flake says the attacks are exaggerated and misleading.

"Some of the accusations about me and veterans' benefits and women's issues and things like that — I think at one time they were saying that Jeff Flake wants to return to the time before women could vote," Flake tells NPR. "That gets personal."

Dr. Cristina Beato, former acting assistant secretary of health between 2003 and 2005, looks into the camera and says Carmona has problems with women, and with anger: "There was an angry pounding on the door in the middle of the night. I'm a single mom. I feared for my kids and for myself. It was Richard Carmona, and I was his boss. Carmona's not who he seems." Beato concludes by saying, Carmona "should never, ever be in the U.S. Senate."

Carmona called Beato troubled and countered with his own ad featuring Kathleen Brennan, a retired police captain who was his SWAT team commander, saying Carmona was a "joy to work with" when he served in the Pima County, Ariz., sheriff's department, and that he "treats everyone with respect."

"When I see a career politician like Jeff Flake attacking Rich Carmona, who has spent his life helping others, it's despicable," Brennan says in the ad.

Carmona didn't help himself in a debate Thursday night when he told the male moderator that he was "prettier" than CNN's Candy Crowley, who moderated Tuesday's presidential debate. Republicans pounced. Carmona apologized.

There's no telling what the effects will be. Early voting has already begun in Arizona.

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MELISSA BLOCK, HOST:

From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.

ROBERT SIEGEL, HOST:

And I'm Robert Siegel. For the first time in nearly a generation, voters in Arizona will elect a new senator. Republican Jon Kyl is retiring, after 18 years. And a lot of people expected another Republican, Congressman Jeff Flake, to win the seat easily. Instead, he finds himself in a tight competition with Democrat Richard Carmona. As we hear from NPR's Ted Robbins, the race has become heated - and on the airwaves, nasty.

TED ROBBINS, BYLINE: Republican Jeff Flake.

(SOUNDBITE OF POLITICAL AD)

ROBBINS: Waking before dawn - in this ad - to go run, eat breakfast with his family, and drive to work. From a pioneering Arizona Mormon family; endorsed by National Right to Life and the NRA.

: Arizona's battle-tested conservative is Jeff Flake.

ROBBINS: If you're into battle-tested, though, Democrat Rich Carmona's resume is hard to beat: born in Harlem, of Puerto Rican descent.

(SOUNDBITE OF POLITICAL AD)

ROBBINS: And as one of Carmona's Vietnam-era colleagues says in this ad, he made the most of it.

: ...became a doctor, a SWAT team leader and surgeon general.

ROBBINS: Jeff Flake and the Republican Party have been tying Rich Carmona to the Obama administration - not necessarily a helpful connection, in a state Mitt Romney is expected to win.

(SOUNDBITE OF POLITICAL AD)

ROBBINS: Carmona, though, served as surgeon general under George W. Bush. Until a year or so ago, he was a registered independent. And in the past, he says Republicans also tried to recruit him for office.

RICH CARMONA: In an old Republican Party, I might have been able to go with a fiscal conservative approach, and smaller government. I'm OK with that. But when you look at what's happened in our state, and the nation, and where the Republican Party has gone; most of my friends who are moderate Republicans, are embarrassed that we're attempting to legislate contraception, defunding Planned Parenthood.

ROBBINS: Carmona is playing the moderate to Jeff Flake's conservative. Sensing a possible upset, the Democratic Party has spent at least $1 million on ads portraying Flake as too conservative, even for Arizona. They've attacked Flake's positions on abortion and contraception, and highlighted a few of his votes on veterans. Flake says the attacks are exaggerated and misleading.

REP. JEFF FLAKE: Some of the accusations about me and veterans' benefits and women's issues, and things like that - I think at one point, they were saying that Jeff Flake wants to return to the time before women could vote; something like that. That gets personal. I'm sorry.

ROBBINS: Last week, conflicting polls showed each candidate slightly ahead. The already tough campaign got really personal. Flake and the Republican Party released an ad aimed at women, attacking Carmona's temperament. Former Bush Health and Human Services official Cristina Beato looks into the camera, and says Carmona has problems with women, and with anger.

(SOUNDBITE OF POLITICAL AD)

ROBBINS: Carmona denied the charges. He called Beato troubled herself; and he countered with an ad featuring his former sheriff's SWAT team captain, Kathleen Brennan, saying Carmona was, quote, "a joy to work with."

(SOUNDBITE OF POLITICAL AD)

ROBBINS: Carmona didn't help himself in the debate last night, when he told the male moderator that the moderator was prettier than CNN's Candy Crowley. Republicans pounced. Carmona apologized. No telling what the effects will be. Early voting has already begun, in Arizona.